Earth Talk: The New Skinny on Dietary Fat

Dear EarthTalk: What's the skinny on fat these days? I saw a major magazine cover image recently that was suggesting fat wasn't so bad for us after all? -- M.B.

Going "fat-free" might seem like an effective, safe way to lose weight when considering that fat contains nine calories per gram, compared to four calories per gram in carbohydrates and proteins. But if you take into account the fact that approximately 60 percent of human brain matter consists of fats, eating reduced fat or fat-free foods high in sugar and refined carbohydrates no longer seems as appealing for our health.

"The brain thrives on a fat-rich, low carbohydrate diet, which unfortunately is relatively uncommon in human populations today," reports David Perlmutter, author of Grain Brain. "Mayo Clinic researchers showed that individuals favoring carbohydrates in their diets had a remarkable 89 percent increased risk for developing dementia as contrasted to those whose diets contained the most fat. Having the highest levels of fat consumption was actually found to be associated with an incredible 44 percent reduction in risk for developing dementia."

Granted, certain types of fats are more beneficial than others. "Good" fats include monounsaturated fats, found abundantly in olive oil, peanut oil, hazelnuts, avocados and pumpkin seeds, and polyunsaturated fats (omega 3 and omega 6), which are found in flaxseed oil, chia seeds, marine algae oil and walnuts.

"In the '70s and early '80sâ€¦we were not talking about low-fat diets. We were talking about replacing saturated fat with a healthy fat, polyunsaturated fat," says Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health. "But somewhere in the mid-1980s, we lost that message. It's perhaps partly because some nutritionists felt it was too complicated to talk about different types of fat, and developed the notion we should just reduce all types of fat across the board."

With over five million Americans currently living with Alzheimer's disease, researchers are examining which dietary fats may help prevent dementia. Olivia Okereke at Brigham & Women's Hospital tested how different types of fats affect cognition and memory in women. Over the course of four years, she found that women who consumed high amounts of monounsaturated fats had better overall cognitive function and memory. A study by researchers from Laval University in Quebec revealed similar findings: Diets high in monounsaturated fats increased the production and release of the neurotransmitter acetylcholine, which is critical for learning and memory. The loss of acetylcholine production in the brain has been associated with Alzheimer's disease.

Unfortunately, canola oil, which is high in monounsaturated fats in its natural form, is often hydrogenated so it can stay fresh longer in processed foods. Partially hydrogenated oils also known as Trans fats were shown to be detrimental to memory in a recent University of California San Diego study. "Trans fats increase the shelf life of the food but reduce the shelf life of the person," reports study author Beatrice Golomb.

Of course, a well-rounded diet with plenty of fruits and vegetables may still be the best way to stay healthy. But it's good to know that a little fat here and there won't kill you. In fact, it might well help you live a healthier, more productive life.